1. Technical Field
The present invention relates to a display device for cargo-handling vehicles, especially for vehicles with a small display device having a small display due to limited space for installing the display device, such as a forklift, in which0 the limited display space can be utilized and the display device displays items in an operation sequence of the cargo-handling vehicle.
2. Description of the Related Art/Background Art
A schematic structure of a forklift as a cargo-handling vehicle shown in FIG. 4 has a vehicle body 72 equipped with front wheels 70 and rear wheels 71, a fork 73 for loading a cargo 86, and a mast consisting of an outer mast 74 and an inner mast 75 for raising and lowering the fork 73, and being provided at the front of the vehicle body 72.
The fork 73 is installed on the mast via lift brackets 76, and the fork is constructed in such way that the outer mast 74 is capable of controlling a position of the cargo 86 forward and backward by tilting the fork 75 forward or backward (tilting operation), and the inner mast 75 being fixed to the top part of the outer mast 74 and being connected to the lift brackets 76 via rails, so as to move the fork 73 having the cargo 86 loaded thereon and the lift bracket 76 in the vertical direction along the rail (lifting operation) by the outer mast 74 and inner mast 75.
The outer mast 74 is capable of controlling the tilt angle around a supporting axis of the outer mast 74 by a tilt cylinder 77. The lift bracket 76 is constructed to move in the vertical direction on the rail of the inner mast 75 via a chain wheel 79 and a chain 80 with the vertical movement of a lift cylinder 78. Thus, the fork 73 for loading the cargo 86 thereon connected to the tip of the lift bracket 76, can be controlled to move forward and backward and up and down
A tilt angle sensor 81 such as a potentiometer, which detects change of the tilt cylinder 77, is provided on the tilt cylinder 77. And a lift sensor such as a wire-type displacement sensor 82, which detects change of the lift cylinder 77 in the vertical direction, is provided on the lift cylinder 78. A hydraulic pressure sensor 85 which measures the hydraulic pressure of the oil being supplied to the lift cylinder 78, is provided on a hydraulic pipe 84 filled with oil 83b for pressurizing the lift cylinder 78. With this structure, the hydraulic pressure in the direction to raise the fork 73 is converted to the weight of the cargo, so as to measure the weight of the cargo 86 loaded on the fork 73.
FIG. 5 is a perspective view of a driving unit of a forklift as a cargo-handling vehicle. The figure shows a handle 90, a display unit 91 for displaying speed, fuel gage, weight of the loaded cargo 86, tilt angle of the mast and the like, a forward-backward lever 92 for shifting gears between forwarding and reversing, a parking-brake lever 93, a lift lever 94 for raising and lowering the fork 73, a tilt lever 95 for controlling the position of the cargo 86 loaded on the fork 73 forward and backward by tilting the mast forward or backward, a brake pedal 96 and an accelerator pedal 97.
FIG. 6 is a diagram to explain an example of operation sequence for moving the cargo 86 by the forklift 72 as a cargo-handling vehicle. As shown in FIG. 6(A) which is a preparation state before loading the cargo 86, the tilt lever 95 is pulled and the mast is tilted backward so as to raise the fork 73 by 15 to 20 cm from the ground. In the state, the forklift 72 drives to the location where the cargos 86 are placed. Next, as shown in FIG. 6(B) the forklift 72 stops where the distance between the front tip of the fork 73 and the cargos 86 is about 20 to 30 cm and the parking-brake lever 93 being pulled to a lock position.
As shown in FIG. 6(C), the mast tilted by operation of the tilt lever 95 is returned to an upright position and being lifted by operation of the lift lever 94 to the same height as an insertion gap of pallets. In the state, as shown in FIG. 6(D), the parking-brake lever 93 is released, the forward-backward lever 92 being moved so as to the forwarding position to move the forklift slowly forward, the fork 73 being inserted between the pallets, the forklift 72 stopping and the parking brake 93 being moved to the lock position.
Next, as shown in FIG. 6(E), the cargo 86 is lifted by about 10 cm with operation of the lift lever 94, and as shown in FIG. 6(F) the tilt lever 95 is pulled so as to tilt the mast backward for a stable transportation of the cargo. In the state, the forward-backward lever 92 is moved to the reverse position, the parking-brake lever 93 being released, the forklift backing up to the location where the cargo 86 can be safely unloaded.
Then, the forklift stopping about 20 to 30 cm away from the stack of remaining cargos 86, the parking-brake lever 93 being locked, and the lift lever 94 being operated as to lower the fork 73 so that the bottom of the fork 73 is about 15 to 20 cm off the ground as shown in FIG. 6(G). In the state, as shown in FIG. 6(H) the forward-backward lever 92 is moved to the reverse position, the parking-brake lever 93 being released so as to back up the forklift to the location where the forklift can safely change the direction, and then the forklift moving to a destination such as to a truck.
These are examples of the schematic structure of the forklift as a cargo-handling vehicle and operation examples of moving the cargos. With this type of forklift, in the case of loading the cargos 86 onto a truck it is preferable to display the weight of the cargo loaded on the forklift while lifting the cargo 86 so as to avoid the total weight of the cargos exceeding the maximum allowable weight of the truck. Moreover, when an entry-level operator operates the forklift, it is hard to visibly confirm a forward or backward tilt of the mast (tilt angle), and thus display of current state of the tilt angle is desired.
In this case, a passenger vehicle has a sufficient space for a display device displaying a variety of information such as vehicle speed, engine rotation, fuel gage, shift lever position, engine coolant temperature, a traveling distance, a light operation mode, an operation mode of a windshield wiper, turn-signal signs, an operation mode of air-conditionings, indoor temperature and the like. However, in a cargo-handling vehicle such as a forklift, visibility from the front is important and as shown in FIG. 5, the display device 91 can only be installed in a small space such as on a front side of the vehicle body with respect to a steering wheel 90, and thus only a small display device with a small display can be installed.
In order to display essential pieces of information in a display device with limited space, Patent Reference 1 (JP5-260605A) proposes a monitor device with alert indications in which when any abnormality is detected in the vehicle, the display is automatically switched to a alarm display showing contents of the abnormality along with alarm, the alarm being turned off by pressing a confirmation key, and the display being returned to a normal display or switched to a detailed display of the abnormality so as to provide sufficient information.
Patent Reference 2 (JP6-67158A) discloses a display device for a vehicle in which for the purpose of easy confirmation of conditions of the vehicle, a multi-display is provided adjacent to a speed indicator which is always on and normally displays a rotation speed of the engine but switched to a warning indication upon receiving signals from a variety of warning sensors in the case of detecting any defects. In a similar manner, the display is changed when a shift lever, light switch or radio switch is turned on.
Furthermore, Patent Reference 3 (JP2003-173210A) proposes a display device in an operating machine such as a combine, in order to display plural types of abnormal information in a LCD display device provided in the combine for easy confirmation of the displayed information. The proposed display device has a CAN controller which shows each piece of the abnormal information sequentially on LCD display panel.
However, all of the display devices disclosed by the cited references have a limited space for a display. The display device of Patent Reference 1 switches the normal display to the alert display indicating details of the detected abnormality. The display device disclosed in Patent Reference 2 switches the display in the case of detecting defects of the parts or operation the shift lever, light switch and radio switch. The display device of Patent Reference 3 switches the display sequentially to show information of abnormality. However, there is no indication of displaying warnings in such a case that an entry-level operator operates the vehicle without following the operation sequence as described above such as driving the forklift while the fork 73 is upright or the mast is tilted forward and the tip of the fork 73 is barely off the ground.
Therefore, an object of the present invention is to provide a display device of a cargo-handling vehicle such as a forklift which can use only a display device with a small display due to a limited space to install the device, wherein the small display space is fully utilized and the operation steps of the cargo-handling vehicles are sequentially displayed in the order of the operation.